The capacity of the machinery to convert energy from mechanical to electrical or vice versa is directly related to the rate of which the excess heat can be removed. Currently, the gas which is used to cool electrical machinery, such as a motor or generator, whether hydrogen or air, is typically cooled by a heat exchanger in the system that transfers the heat to a fluid such as water or anti-freeze mixture. This coolant then rejects the heat to the atmosphere through a second heat exchanger. Therefore, the cooling capacity is limited by the temperature of the heat sink. In hot climate regions of the world, this severely reduces the cooling capacity and limits generator/motor capability.
Duplex series coolers are currently used on generators ranging from 25 MW to 1300 MW. Coolant supplied to these coolers comes from a common "ambient following source." Assuming the two cooler sections are constructed with identical hardware (for example, tube and fin count), the first section removes about 75% of the heat load, and the second section removes the remaining 25%, i.e., the gas flows over the heat exchangers "in series." Every effort has been made to reduce the approach temperature difference between the cold liquid temperature and ambient temperature, and between the generator cold gas and cold liquid temperature using extended tube and fin technology. This closes the gap between the generator cold gas and ambient air temperature, but the generator output is still limited by the temperature of the ambient following source.
Chillers have been applied to generators in the past, but not as described herein where the chiller technology is used to step cool the gas in a duplex series cooler arrangement.